The present invention relates to a semiconductor device, and more specifically, to a semiconductor device provided with a function for detecting the temperature of a semiconductor element or the ambient temperature of a semiconductor element.
Japanese Patent No. 2630242 describes an example of a semiconductor device that prevents breakage of a semiconductor element when the temperature of the activated semiconductor element increases to an abnormal level. The semiconductor device includes a heat sensing element in addition to the semiconductor device. When there is an abnormal increase in the temperature of the semiconductor device, the heat sensing element detects the temperature increase and generates a detection signal. The semiconductor device deactivates the semiconductor element in response to the detection signal to avoid thermal breakage.
Referring to FIG. 1, the semiconductor device includes a MOS transistor 40 and a diode 41, which functions as a heat sensing element and which is formed near the MOS transistor 40. The semiconductor device detects the ambient temperature of the diode 41 by measuring the voltage in the forward direction as forward current flows through the diode 41.
When designing a semiconductor device, electrostatic discharge (ESD) resistance must be taken into consideration. Electrostatic discharge refers to static electricity. When static electricity is applied to the terminal of the semiconductor device, surge current flows through the semiconductor device. The surge current may affect the elements of the semiconductor device in an undesirable manner.
The semiconductor device described in Japanese Patent No. 2630242 includes a protection diode 42 connected parallel to the temperature detection diode 41 in an opposite direction to increase the ESD resistance of the temperature detection diode 41. In this configuration, when electrostatic discharge is applied to an anode terminal 41a of the diode 41 (i.e., when electrostatic discharge is applied such that the potential at the anode terminal 41a becomes greater than the potential at a cathode terminal 41b), current resulting from the electrostatic discharge flows through the temperature detection diode 41. When electrostatic discharge is applied to the cathode terminal 41b of the diode 41 (i.e., when electrostatic discharge is applied such that the potential at the cathode terminal 41b becomes greater than the potential at the anode terminal 41a), current resulting from the electrostatic discharge flows through the protection diode 42. This prevents reverse voltage from being applied to the temperature detection diode 41. As a result, the ESD resistance of the temperature detection diode 41 is increased.
However, due to leakage current flowing through the protection diode 42, which is connected to the diode 41 in the opposite direction, the temperature detection accuracy is lowered.